The number of sport, professional and commercial divers is on the increase. Danger is ever present to all divers. The need to communicate between divers can vary from casual to life-threatening. Hand signals would be satisfactory if divers were always within reach of each other or always within one another's field of vision. Even when divers are separated by short distances hand signals can lack the ability to create attention and can be misread with results that include serious consequences. Thereafter, inventors have attempted to create a reliable and effective attention arresting sound generating apparatus. Electronic and electro-mechanical devices put themselves in immediate question because their intended use subjects them to a substantially hostile environment. Also, accidental damage to the housing can result from routine diver activity causing the housing to leak thereby rendering the device useless. Routine maintenance inspections, including battery replacement increase the human error factor thereby adding to the question of ongoing reliability. Those electronic and electro-mechanical devices which are manufactured in an attempt to most nearly overcome these shortcomings cost more to manufacture making them expensive to own. Accordingly, a manually operated signaling device is capable of providing desirable results at low end-user cost because simplicity of design makes it cheaper to manufacture.
One such device is found in the underwater signaling device of Oehme et al, U.S. Pat. No. 5,187,691 issued Feb. 16, 1993. Oehme discloses a water-tight cylindrical chamber with an end member at each end and containing therein a metal ball. The cylindrical chamber and end members are polyvinyl chloride commonly called PVC. The end members are covered with an outer surface one of which has a loop to receive a cord. Also, a foam sleeve is also provided over the cylindrical chamber so as to provide improved underwater hand holding ability. To signal with this apparatus a person shakes it back and forth causing the metal ball to strike the perpendicular surface of the end members. Oehem repeatedly describes the resulting sound as a rattle, wherein a rattle is usually defined as a succession of short sharp sounds.
This signaling device is flawed in several ways. The cylindrical chamber and end members are made of PVC which is substantially softer than the steel ball. The interior perpendicular surface of the end member walls directly receive the full impact of the steel ball. The ball being round has a very small point of contact at the perpendicular surfaces. The resulting sound of the steel ball striking the much softer PVC can only be described as a non-reverberating thud. Oehem covers the end members with an outer surface plus a foam sleeve over the entire length of the cylindrical chamber. This foam sleeve is intended for improved underwater handling. Notably, foam materials are used extensively for insulating against high and low temperatures. Also, textured foam and sheet foam are particularly effective in creating a sound deadening environment. While the hand holding aspect may be improved the foam sleeve and outer coverings of the end members definitely muffles the sought after end result, e.g. audible sound. Even with the end member coverings and foam sleeve removed the sound generated by Oehem's apparatus could not be recognized as a rattle (e.g. sharp sound). The sound would still be more of a non-resonating thud able to carry only a short distance. It is my opinion that the molecular structure of the PVC will detrimentally change as a result of being battered by the steel ball. Additionally, it is my opinion that heat is produced from the repeated battering causing the PVC to become more and more brittle until the PVC ruptures rendering the device useless.